真空蒸发CdSe_(1-x)Te_x薄膜的光电导特性

PHOTOCONDUCTING PROPERTIES OF VACUUM-EVAPORATED CdSe_(1-x)Te_x THIN FILM

本文采用CdSe和CdTe混合物作为真空蒸发源材料,制备了CdSe_(1-x)、Te_x(0<X<0.3)光电导薄膜,并在氩气氛中热处理。研究了这种薄膜的结构,光敏性与材料组分及热处理的关系。

CdSe1-x Tex photoconductive films were prepared by the vacuum-evaporated method using the mixture of CdSe and CdTe.The photoconducting properties of CdSe1-xTex films (thickness about treated at the temprature of 550-650℃ were investigated.CdSe and CdTe powders were deposited onto the chemically cleaning glass or quartz substiates at the temperature of 100-150℃ and in vacuum of 10-5 Torr.Indium used as electiodes were then evaporated onto the CdSe1-x Tex film. The gap between the electrodes was 0.5mm. The slructuie of thin films by X-ray analysis is shown in Fig. 1.Films of CdSe1-x Tex are the mixture of the amorphous and microcrystal before heat treatment. It is obvious that the size of costal particle increases after heat treatment. The influences of the heat treatment temperature on the ratio of dark lesistance RD to the light resistance RL are shown in Fig.3. It is seen that the film resistance ratio RD/RL attains to 106 when the lemperatme of the heat treatment is 625癈. The observed photosensi-tivily is obviously reduced when the temperature of the heat treatment is lo, er than 580℃.There are a lot of crystalline particle boundaries and amorphous structure in the untreated CdSe1-xTex film. The barrier at particle boundanies, therefore, decreases the mobility of carrier for the carrier scattering.Amorphous structure causes a lot of localization stales in the bandgap. The localization states play an important role in the electron trap and the recombination centers decrease the lifetime of carrier. These factors reduce the photoelectric sensitivity.The ratio of dark-to-light resistance in obtained films is in 106-107 orders of magnitude. Fig.5 shown the spectrum response curves of CdSe1-xTex and CdSe. The peaks of spectrurm response of these films are 7400A 8200A and 8600A (curve 1, 2, 3) respectively, but the response peak cf CdSe film is 7000 A (curve 4).Among the samples of CdTe-doped CdSe the sample A is optimum in terms of CdTe content.